Differential/ratiometric electromyographic bio-feedback monitor

ABSTRACT

A physiotherapy device for human beings having two parallel measuring channels for indicating the muscle tension in two selected muscles. The device computes and displays the absolute value of each measurement of muscle tension, the arithmetic difference between each measurement and the ratio between each measurement. In operation, the patient observes his own muscle tension readings and responds accordingly in a biological feedback.

' United States Patent Freeman Nov. 4, 1975 MONITOR [75] Inventor: JamesAlbert Freeman, Kensington,

Calif. [73] Assignee: FSW Associates, Kensington, Calif.

[22'] Filed: June 13, 1974 [21] Appl. No.: 478,915

[52] US. Cl. 128/2.1 M; 128/2 S [51] Int. Cl. A61B 5/05 [58] Field ofSearch 128/2.1 R, 2.1 M, 2.1 Z, 128/2 S, 2.1 B; 23/379 [56] ReferencesCited UNITED STATES PATENTS 3,221,731 12/1965 Annis 128/2.1 R 3,621,83611/1971 Nagatomi 3,641,993 2/1972 Gaarder et al. 128/2.1 M

FOREIGN PATENTS OR APPLICATIONS 124,581 3/1959 U.S.S.R. l28/2.l M1,504,205 12/1966 France 128/2.1 M

179,415 8/1964 U.S.S.R. 128/2 S OTHER PUBLICATIONS RECTIFIER Vol. 8, No.2, Mar.-Apr. 1974, p. 127.

Kwatny et a1., Application of Sig. Processing Techniques. Myo-Signels,IEEE Trans. on Bio-Med. Eng, Vol. 17, No. 4, Oct, 1970, pp. 303-313.Basmgjian, Six Channel Electromyograph for Studies on Muscles, IRETrans. on Med. Elec., pp. 45-47, July, 1958.

Molcho et al., Elec. Measurement of Achilles Tendon Reflex, IEEE Trans.on Bio-Med. Eng, Oct. 1971, pp. 353-355.

Primary ExaminerRichard A. Gaudet Assistant ExaminerLee S. CohenAttorney, Agent, or Firm--Flehr, Hohbach, Test, Albritton & Herbert [57]ABSTRACT A physiotherapy device for human beings having two parallelmeasuring channels for indicating the-muscle tension in two selectedmuscles. The device computes and displays the absolute value of eachmeasurement of muscle tension, the arithmetic difference between eachmeasurement and the ratio between each measurement. In operation, thepatient observes his own muscle tension readings and respondsaccordingly in a biological feedback.

10 Claims, 1 Drawing Figure L-CHANNEL A DIFFERENTIAL AMPLIFIER w 4o L-ELECTRONIC DIVIDER *B US. Patent Nov. 4, .1975

llllllll-IL DIFFERENTIAL/RATIOMETRIC ELECTROMYOGRAPHIC BIO-FEEDBACKMONITOR BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention relates to devices for performing physical therapy on humanbeings, and more particularly to devices for performing human musclerehabilitation therapy.

2. Description of the Prior Art In recent years there has been asubstantial amount of research being conducted in the area ofbio-feedback systems. The general concept of a bio-feedback systemincludes the steps of electronically measuring some physiologicalactivity of a patient, translating these measurements into signalsreadily observable by the patient, and then having the patient attemptto control his physiological activity by responding to the observedsignals. In a bio-feedback system the patient actually becomes part ofthe signal transmission circuit. He generates the signals by his ownbodily activity, observes the measured signals either visually, audiblyor tactually, and then in the manner of a feedback loop tries to controlhis bodily activity as indicated by the signals.

Currently, most of the bio-feedback research and experimentation isdirected to the study of the brainwaves that are generated in the humanmind. The human brain waves are recorded on an electroencephalograph(EEG) and displayed to the patient through various electrical circuits.A further discussion of how these measurements are performed and thedevices used to record electroencephalographic activity is contained inthe U.S. Patent Application entitled BIOLOGICAL FEEDBACK SYSTEMS, Ser.No. 299,774, filed Oct. 24, 1972 by James A. Freeman now abandoned.

In the area of physical therapy and human muscle rehabilitation,bio-feedback systems have been used with some success. It has been foundexperimentally that the tension of a muscle is proportional to theelectrical activity of the neuron fibers within that muscle. Thiselectrical activity can be measured by two electrodes placed on the skinof the patient proximate to the muscle. The electrodes produce very weaksignals that musts be greatly amplified. The amplified signals are thenfed to an indicator that displays to the patient the relative tension ofthe muscle being measured. The patient tries to control the muscle byresponding to the signals displayed on the indicator and thereby learnsthrough the feedback to voluntarily relax or to tense the muscle.

Heretofore, these prior art systems have incorporated only a singlefeedback loop and have been found to be inadequate to treat cases ofsevere muscle disorder. In the case of severe muscle disorder, theprocess of learning to tense or relax a disabled muscle is accompaniedby an undesirable, simultaneous tensing or re- SUMMARY OF THE INVENTIONThe differential/ratiometric electromyographic biofeedback monitor is atwo-channel bio-feedback system providing simultaneous measurement andfeedback information on more than one muscle of a patient at one time.In the system a plurality of electrodes are connected to the variousmuscles being studied to measure the relative tension of each. Thesystem displays to the patient the absolute value of each measuredmuscle tension signal, the difference between each muscle tensionsignal, and the quotient of the muscle tension signals.

The primary object of the present invention is to display to the patientthe measured values of the differences and ratios of the tension ofselected muscles so that the patient can gain independent control ofthose muscles which do not interact with each other and can gaincomplimentary control of those muscles which should normally interact.

Additional objects and features of the present invention will appearfrom the following description in which the preferred embodiment of theinvention has been set forth in detail in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic view of adifferential/ratiometric electromyographic bio-feedback monitoraccording to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, referencenumeral 12 indicates a patient undergoing biological feedbackphysiotherapy while lifting a ball 14 in his left hand. Attached to thebiceps of his upper left arm are two electrodes 16 and attached to thetriceps of his upper left arm are two similar electrodes 18. Each set ofelectrodes is placed in proximity to the muscle desired to be monitored;in FIG. 1 the electrodes 16 are measuring the left biceps and theelectrodes 18 are measuring the left triceps.

Each pair of electrodes measures a small electrical potential, called anelectromyographic signal, generated by the neuron fibers within themuscle being measured. Each set of electrodes is connected to a separatehigh gain amplifier 20. The electrical potential measured by each pairof electrodes is in the range of microvolts, so a high gain amplifier isrequired in order to provide a usable signal.

The output of each high gain amplifier 20 is connected to apotentiometer 22 for adjusting the magnitude of the output of each highgain amplifier. Since each muscle being measured by the bio-feedbacksystem produces a signal of a different magnitude, the potentiometersare used to adjust the relative magnitudes of the signals and to give aweighting factor to each muscle. The output of each potentiometer 22 isconnected to a rectifier 24 that converts the signal into a directcurrent signal level proportional to the absolute value of the measuredelectromyographic activity.

Referring to FIG. 1, the electromyographic bio-feedback system includestwo parallel measuring channels, each having a high gain amplifier 20, apotentiometer 22 and a rectifier 24. Each channel separately andindependently measures the electromyographic activity of a selectedmuscle. For the purposes of identification, the electromyographicactivity of the bicep muscle is measured by channel A, and theelectromyographic activity of the tricep muscle is measured by channelB. The duplicate components of channel A contained in channelB areidentified by corresponding primed reference numerals. 1 The outputs ofthe two measuring channels A, B are displayed on an indicator console 26observable by the patient 12. The output from the rectifier 24 ofchannel A is connected directly to an absolute value indicator 28 andalso to a differential amplifier 30 and an electronic divider 32. Theabsolute value indicator 28 is a meter on the indicator console 26displaying the relative value of the muscle tensions measured by channelA. The rectifier 24' of channel B is connected directly to an absolutevalue indicator 34 and also to the differential amplifier 30 and theelectronic divider 32. The absolute value indicator 34 is identical withthe absolute value indicator 28 and displays the relative value of themuscle tension measured by channel B. The differential amplifier 30 is aconventional differential amplifier that generates an outputproportional to the arithmetic difierence between the inputs fromchannel A and from channel B. The output of the differential amplifier30 is connected to a difference indicator 36 which visually indicatesthe absolute value of the quantity (A B) to the patient. The electronicdivider 32 is a conventional electronic dividing circuit that generatesan output proportional to the ratio of the inputs from channel A andfrom channel B. The output of the electronic divider is connected to aratiometric indicator 40 which visually indicates the quotient (A/B) tothe patient.

In operation each pair of electrodes 16, 18 is attached to the skin ofthe patient proximate to the respective muscle being measured.Thereafter the patient begins his muscle conditioning exercise. As eachmuscle tenses and relaxes, each set of electrodes measures theelectromyographic activity in the respective muscle. Theelectromyographic signals from each set of electrodes is amplified inthe high gain amplifier 20,

, rectified in the rectifier 24 and displayed on the indicator console26. As soon as an output is displayed on the indicator console 26, thepotentiometers 22 are adjusted to compensate for the varying magnitudesof the electromyographic signals received from the musclesbeing'measured. The indicator console 26 is located in front of thepatient 12 so that he may observe'the signals visually displayedthereon. As the patient 12 exercises, he tries to control the tension ofthe muscles in his arm in response to the signals visually displayed onthe indicator console 26. The program of muscle conditioning exercisesincludes directions from a physical therapist expressed in terms of thevisual indications displayed on the indicators 28, 34, 36 and 40. Thesedirections incorporate both the absolute value readings as well astheratiometric and difference readings.

It should be appreciated that the patient 12 can measure simultaneouslytwo interacting muscles and the electromyographic bio-feedback monitorcan display the amount of interaction therebetween. the patient can thusgain control of his muscles by observing the visual display andresponding thereto.

While a specific disclosure and embodiment has been shown herein, itshould be realized that many modifications and changes can be made bythose skilled in the art without departing from the spirit of thepresent invention. For example, the visual indicators28, 34, 36 and 40can be replaced by a plurality of galvanometers, colored lights, audiooscillators or any other form of 4 audio, visual, tactile or perceptiblestimulus. Accordingly, the scope of this invention should be understoodin a broader context limited only by the following claims as interpretedin the light of the foregoing example.

I claim:

1. Apparatus for performing biofeedback physical therapy on a humanbeing, comprising means for measuring the relative tension in a firstmuscle of the human being, means for measuring simultaneously therewiththe relative tension in a second muscle of the same human being, meansfor independently amplifying the tension measurements of the first andsecond muscles, means for indicating to the human being in real time theinstantaneous value of the tension measurements of the first and secondmuscles so that the human being can control the muscles being measuredin response thereto, said indicating means incuding means for computingan instantaneous ratiometric value from the two tension measurements andmeans for displaying in real time said ratiometric value to the humanbeing being measured.

2. Apparatus for performing biofeedback physical therapy on a humanbeing, comprising means for measuring the relative tension in a firstmuscle of the human being, means for measuring simultaneously therewiththe relative tension in a second muscle of the same human being, meansfor independently amplifying the tension measurements of the first andsecond muscles, means for indicating to the human being in real time theinstantaneous value of the tension measurements of the first and secondmuscles so that the human being can control the muscles being measuredin response thereto, said indicating means including means for computingan instantaneous arithmetic difference value from the two tensionmeasurements and means for displaying in real time said value to thehuman being being measured.

3. Apparatus for performing biofeedback physical therapy on a humanbeing, comprising means for measuring the relative tension in a firstmuscle of the human being, means for measuring simultaneously therewiththe relative tension in a second muscle of the same human being, meansfor independently amplifying the tension measurements of the first andsecond muscles, means for indicating to the human being in real time theinstantaneous value of the tension measurements of the first and secondmuscles so that the human being can control the muscles being measured Iin response thereto, said indicating means including means for computingboth a ratiometric value and an arithmetic difference value from the twotension measurements and means for displaying in real time simultachableon a human being to provide an output signal indicating the tension of aseparate muscle; 4

b. two high gain amplifiers, each amplifier connected to one set ofelectrodes for amplifying the output signal therefrom;

c. two potentiometers, each connected to one of the high gain amplifiersfor adjusting the output signal therefrom; a

d. two rectifiers, each connected to one of the potentiometers forrectifying the output signal therefrom;

e. a differential amplifier connected to the rectifiers and generatingan output signal proportional to the arithmetic difference between thetwo signals indicating muscle tension;

f. an electronic divider connected to the rectifiers and generating anoutput signal proportional to the quotient of the two signals indicatingmuscle tension; and

g. indicator means observable by the human being being measured andselectably connectable to the output of the differential amplifier andto the output of the electronic divider for displaying in real time theinstantaneous value of the amount of interaction between the separatemuscles.

5. Apparatus of claim 4 wherein the indicator means includes twoindicators, one indicator connected to the output of the differentialamplifier and the other indicator connected to the output of theelectronic divider, permitting the human being being measured to observesimultaneously the amount of interaction between the two musclesdisplayed on the two indicators.

6. Apparatus for conducting biofeedback physical therapy on human beingsby measuring the relative tension of muscles comprising:

a. two sets of electrodes, each electrode set being attachable on ahuman being to provide an output signal indicating the tension of aseparate muscle;

b. two high gain amplifiers, each amplifier connected to one set ofelectrodes for amplifying the output signal therefrom;

c. two potentiometers, each connected to one of the high gain amplifiersfor adjusting the output signal therefrom;

d. two rectifiers, each connected to one of the potentiometers forrectifying the output signal therefrom;

e. two absolute value indicators, each connected to one of therectifiers for displaying to the human being being measured the absolutevalue of the muscle tension signal;

f. a differential amplifier connected to the rectifiers and generatingan output signal proportional to the arithmetic difference between thetwo signals indicating muscle tension; and

g. a difference indicator observable by the human being being measuredand connected to the output of the differential amplifier for displayingin real time the instantaneous value of the arithmetic differencebetween the values of the two muscle tension signals.

7. Apparatus for conducting biofeedback physical therapy on human beingsby measuring the relative tension of muscles, comprising:

a. two sets of electrodes, each electrode set being attachable on ahuman being to provide an output signal indicating the tension of aseparate muscle;

b. two high gain amplifiers, each amplifier connected to one set ofelectrodes for amplifying the output signal therefrom;

c. two potentiometers, each connected to one of the high gain amplifiersfor adjusting the output signal therefrom;

d. two rectifiers, each connected to one of the potentiometers forrectifying the output signal therefrom;

c. two absolute value indicators, each connected to one of therectifiers for displaying to the human being being measured the absolutevalue of the muscle tension signal;

f. an electronic divider connected to the rectifiers and generating anoutput signal proportional to the quotient of the two signals indicatingmuscle tension; and

g. a ratiometric indicator observable by the human being being measuredand connected to the output of the electronic divider for displaying inreal time the instantaneous value of the quotient of the two values ofthe two muscle tension signals.

8. Method of performing biofeedback physical therapy on a human beingcomprising the steps of measuring the relative tension in a first muscleof the human being, measuring simultaneously therewith the relativetension in a second muscle of the same human being, independentlyamplifying the tension measurements of the first and second muscles,indicating to the human being in real time the instantaneous value ofthe tension measurements of the first and second muscles -so that thehuman being can control the muscles being measured in response thereto,and further in which said step of indicating the tension measurementsincludes computing an instantaneous ratiometric value from the twotension measurements and displaying in real time said ratiometric valueto the human being being measured.

9. Method of performing biofeedback physical therapy on a human being,comprising the steps of measuring the relative tension in a first muscleof the human being, measuring simultaneously therewith the relativetension in a second muscle of the same human being, independentlyamplifying the tension measurements of the first and second muscles,indicating to the human being in real time the instantaneous value ofthe tension measurements of the first and second muscles so that thehuman being can control the muscles being measured in response thereto,and further in which said step of indicating the tension measurementsincludes computing an instantaneous arithmetic difference value from thetwo tension measurements and displaying in real time said value to thehuman being being measured.

10. Method of performing biofeedback physical therapy on a human beingcomprising the steps of measuring the relative tension in a first muscleof the human being, measuring simultaneously therewith the relativetension in a second muscle of the same human being, independentlyamplifying the tension measurements of the first and second muscles,indicating to the human being in real time the instantaneous value ofthe tension measurements of the first and second muscles so that thehuman being can control the muscles being measured in response thereto,and further in which said step of indicating the tension measurementsincludes computing both a ratiometric value and an arithmetic differencevalue from the top tension measurements and displaying in real timesimultaneously said values to the human being being measured.

1. Apparatus for Performing biofeedback physical therapy on a humanbeing, comprising means for measuring the relative tension in a firstmuscle of the human being, means for measuring simultaneously therewiththe relative tension in a second muscle of the same human being, meansfor independently amplifying the tension measurements of the first andsecond muscles, means for indicating to the human being in real time theinstantaneous value of the tension measurements of the first and secondmuscles so that the human being can control the muscles being measuredin response thereto, said indicating means incuding means for computingan instantaneous ratiometric value from the two tension measurements andmeans for displaying in real time said ratiometric value to the humanbeing being measured.
 2. Apparatus for performing biofeedback physicaltherapy on a human being, comprising means for measuring the relativetension in a first muscle of the human being, means for measuringsimultaneously therewith the relative tension in a second muscle of thesame human being, means for independently amplifying the tensionmeasurements of the first and second muscles, means for indicating tothe human being in real time the instantaneous value of the tensionmeasurements of the first and second muscles so that the human being cancontrol the muscles being measured in response thereto, said indicatingmeans including means for computing an instantaneous arithmeticdifference value from the two tension measurements and means fordisplaying in real time said value to the human being being measured. 3.Apparatus for performing biofeedback physical therapy on a human being,comprising means for measuring the relative tension in a first muscle ofthe human being, means for measuring simultaneously therewith therelative tension in a second muscle of the same human being, means forindependently amplifying the tension measurements of the first andsecond muscles, means for indicating to the human being in real time theinstantaneous value of the tension measurements of the first and secondmuscles so that the human being can control the muscles being measuredin response thereto, said indicating means including means for computingboth a ratiometric value and an arithmetic difference value from the twotension measurements and means for displaying in real timesimultaneously said values to the human being being measured. 4.Apparatus for conducting biofeedback physical therapy on human beings bymeasuring the relative tension of muscles, comprising: a. two sets ofelectrodes, each electrode set being attachable on a human being toprovide an output signal indicating the tension of a separate muscle; b.two high gain amplifiers, each amplifier connected to one set ofelectrodes for amplifying the output signal therefrom; c. twopotentiometers, each connected to one of the high gain amplifiers foradjusting the output signal therefrom; d. two rectifiers, each connectedto one of the potentiometers for rectifying the output signal therefrom;e. a differential amplifier connected to the rectifiers and generatingan output signal proportional to the arithmetic difference between thetwo signals indicating muscle tension; f. an electronic dividerconnected to the rectifiers and generating an output signal proportionalto the quotient of the two signals indicating muscle tension; and g.indicator means observable by the human being being measured andselectably connectable to the output of the differential amplifier andto the output of the electronic divider for displaying in real time theinstantaneous value of the amount of interaction between the separatemuscles.
 5. Apparatus of claim 4 wherein the indicator means includestwo indicators, one indicator connected to the output of thedifferential amplifier and the other indicator connected to the outputof the electronic divider, permitting the human being being measured toobserve simultaneously the amount of interactIon between the two musclesdisplayed on the two indicators.
 6. Apparatus for conducting biofeedbackphysical therapy on human beings by measuring the relative tension ofmuscles comprising: a. two sets of electrodes, each electrode set beingattachable on a human being to provide an output signal indicating thetension of a separate muscle; b. two high gain amplifiers, eachamplifier connected to one set of electrodes for amplifying the outputsignal therefrom; c. two potentiometers, each connected to one of thehigh gain amplifiers for adjusting the output signal therefrom; d. tworectifiers, each connected to one of the potentiometers for rectifyingthe output signal therefrom; e. two absolute value indicators, eachconnected to one of the rectifiers for displaying to the human beingbeing measured the absolute value of the muscle tension signal; f. adifferential amplifier connected to the rectifiers and generating anoutput signal proportional to the arithmetic difference between the twosignals indicating muscle tension; and g. a difference indicatorobservable by the human being being measured and connected to the outputof the differential amplifier for displaying in real time theinstantaneous value of the arithmetic difference between the values ofthe two muscle tension signals.
 7. Apparatus for conducting biofeedbackphysical therapy on human beings by measuring the relative tension ofmuscles, comprising: a. two sets of electrodes, each electrode set beingattachable on a human being to provide an output signal indicating thetension of a separate muscle; b. two high gain amplifiers, eachamplifier connected to one set of electrodes for amplifying the outputsignal therefrom; c. two potentiometers, each connected to one of thehigh gain amplifiers for adjusting the output signal therefrom; d. tworectifiers, each connected to one of the potentiometers for rectifyingthe output signal therefrom; e. two absolute value indicators, eachconnected to one of the rectifiers for displaying to the human beingbeing measured the absolute value of the muscle tension signal; f. anelectronic divider connected to the rectifiers and generating an outputsignal proportional to the quotient of the two signals indicating muscletension; and g. a ratiometric indicator observable by the human beingbeing measured and connected to the output of the electronic divider fordisplaying in real time the instantaneous value of the quotient of thetwo values of the two muscle tension signals.
 8. Method of performingbiofeedback physical therapy on a human being comprising the steps ofmeasuring the relative tension in a first muscle of the human being,measuring simultaneously therewith the relative tension in a secondmuscle of the same human being, independently amplifying the tensionmeasurements of the first and second muscles, indicating to the humanbeing in real time the instantaneous value of the tension measurementsof the first and second muscles so that the human being can control themuscles being measured in response thereto, and further in which saidstep of indicating the tension measurements includes computing aninstantaneous ratiometric value from the two tension measurements anddisplaying in real time said ratiometric value to the human being beingmeasured.
 9. Method of performing biofeedback physical therapy on ahuman being, comprising the steps of measuring the relative tension in afirst muscle of the human being, measuring simultaneously therewith therelative tension in a second muscle of the same human being,independently amplifying the tension measurements of the first andsecond muscles, indicating to the human being in real time theinstantaneous value of the tension measurements of the first and secondmuscles so that the human being can control the muscles being measuredin response thereto, and further in which said step of indicating thetension measurements Includes computing an instantaneous arithmeticdifference value from the two tension measurements and displaying inreal time said value to the human being being measured.
 10. Method ofperforming biofeedback physical therapy on a human being comprising thesteps of measuring the relative tension in a first muscle of the humanbeing, measuring simultaneously therewith the relative tension in asecond muscle of the same human being, independently amplifying thetension measurements of the first and second muscles, indicating to thehuman being in real time the instantaneous value of the tensionmeasurements of the first and second muscles so that the human being cancontrol the muscles being measured in response thereto, and further inwhich said step of indicating the tension measurements includescomputing both a ratiometric value and an arithmetic difference valuefrom the top tension measurements and displaying in real timesimultaneously said values to the human being being measured.